Years ago, California passed Prop 65 that requires warning labels on many products. Here is a pretty good article that explains it in layman's terms:
http://thechart.blogs.cnn.com/2008/1...e-for-concern/
In California, you get used to seeing these warnings, as they are on almost everything! Just use what you are comfortable with.
I just use an old cloth napkin or light-weight towel. I can't see through it, but I haven't had a problem yet.
You can always try contacting the manufacturer and explain what happened. In many states you are not required to have the receipt.